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Batman - A Delta Wing (Part 1)
"Batman" is the name used in motorsport for the peculiar wings, triangular in shape, that most of the Formula 1 cars used, until 2008, placed ahead of the rear wheels.
The way it operates has little to do with a conventional wing and its base concept originated in the delta wings of supersonic fighter aircraft.
In the mid-eighties it began to be used on the side pods of the IndyCar, small aerodynamic devices in the form of inverted delta wings, whose aim was to take advantage of the free space left in the sidepods, narrowed in that area, to obtain some additional downforce.
This was the start of the single setter use of a concept of wing that was originally developed for supersonic aircraft and later used in the "space shuttle” that had, until then, limited application in racing cars.
The concept of delta wing had been, since the sixties, used discreetly, as small fins, called "dive plates", applied to the bodywork of the GT and Sport- Prototypes cars, in order to balance the downforce of these vehicles.
The delta wing, designated by its triangular shape, when used upside down and positioned in an angle of attack with respect to the air flowing over it, as can be seen in drawing 2a, will induce the formation of a vortex in the underside of the wing, which develops along its free edge (the other is attached to the bodywork) and moving along this edge in the entire length of the wing.
This vortex is created by the sudden inflection of the airflow to overcome the leading edge of the wing.
The vortex thus generated will be stronger the more sharp is the leading edge and the greater the angle of attack. The drag caused by such wings is smaller in the case of a delta wing with rounded leading edge, as used in the "space shuttle", but in these wings, the induced vortices have lower strength.
This vortex is being boosted, in its path along the underside of the wing, by the inflow of new air flows ranging flowing along the wing’s leading edge and that will feed the growing vortex.
The vortex airflow is rotating on itself at a very high speed. Since we know that the pressure in airflow is inversely proportional to its velocity, we can easily imagine that it will induce a negative lift force applied along the entire free edge of the lower face of this delta wing.
In the remaining area of the lower surface of the wing, limited externally by the vortex, the air flows smoothly and linearly, as if it were a conventional wing and, as can be seen in drawings 2a and b, inducing a negative lift of considerably less force than the one produced by the vortex.
In drawing 2b we can compare the negative aerodynamic load difference induced by these two types of flow on the lower surface of a delta wing and may also observe the gain in strength of the vortex, then of the force induced in the wing by the vortex, when the external delta wing edge is in additional angle with respect to the airflow.
When compared with a traditional wing, the delta wing is less effective, not only because it requires a greater angle of attack to achieve similar aerodynamic loads, but also because the drag produced for the induction load is higher than that of a conventional wing.
The great advantage of the delta wing is that of maintaining effective, with adherent airflow in the lower face, when working under turbulent airflows and at angles of attack higher than tolerated by a traditional wing, which loss would occur at an angle of attack in which the delta wings usually are more effective.
The drag produced by this type of wing is, as stated above, higher than by a conventional wing, but the fact that their effectiveness is due to the vortex created in it, allows it to remain effective when crossed by turbulent airflows.